Climate change could cause sex switch in crocs

Warming climate could cause a sex imbalance in crocodiles making it more difficult to find mates, according to a south African scientist.

Dr. Alison Leslie, a prefessor at South Africa’s University of Stellenbosch, said that crocodile gender is determined by embryo temperature during incubation and that higher temperatures could skew the sex ratio of populations.

“A difference of 0.5 – 1ºC in incubation temperature results in markedly different sex ratios,” said Leslie, principal investigator of the ‘Crocodiles of the Okavango Delta’ project organized by the Earthwatch Institute, a global volunteer organization that supports scientific field research by offering members of the public opportunities to work alongside leading field scientists and researchers. “Research shows that nest temperatures of about 32-33 degrees Celsius result in males, while temperatures higher and lower result in females. Temperatures within a nest can vary from the top to the bottom of the nest, and can result in mixed-gender hatchlings. ”

Nile crocodiles are among the fiercest predators in the Okavango Delta, Botswana, yet their population has shrunk due to habitat loss and hunting. Dr. Alison Leslie of University of Stellenbosch suggests that climate change will be a further setback to crocodile numbers. Photo by Oscar Baldomero.

“More female hatchlings due to the cooler or hotter incubation temperatures could lead to eventual extirpation of the species from an area,” added Leslie. “Even though crocodilians have been around for millions of years, and as important as these creatures may be in the systems they occupy, they are a much understudied species,”

Leslie made her comments during the filming of A Year on Earth, premiering this week on Discovery Kids Channel.